(JTA) – Police in Crimea, a territory that Russia annexed from Ukraine in 2014, are investigating the desecration by robbers of a mass grave of Holocaust victims near the city of Simferopol.

The investigation opened Tuesday following the unauthorized exhumations performed last week at the site of a firing trench, where Nazis and their collaborators killed hundreds of Jews, the TASS news agency reported.

“A local resident saw at night strangers digging and immediately informed us,” Anatoly Gendin, head of the Association of Jewish Organizations and Communities of Crimea, told the news agency. His organization also complained to police about the dig, which he said were likely the work of robbers looking for precious items.

The incident, the second case of its kind in five years in Crimea, came amid preparations for enclosing burial sites whose locations are known with concrete enclosures.

“There is a preliminary decision of the Crimea State Committee and Jewish community organizations on setting up concrete enclosures and establish there a surveillance system,” Grigory Ioffe, a deputy speaker of the parliament of Crimea, which is one of Russia’s semi-autonomous regions, told TASS.

The Germans captured Simferopol on November 1, 1941, when it had approximately 12,000 Jews including many Krymchaks, the name of a nearly-extinct ethnic group of Jews of Turkmen decent who had lived in Crimea for many centuries before the Holocaust.

They were ordered to wear white armbands with a Star of David on both sleeves or on their chests, according to the Yad Vashem Holocaust museum in Jerusalem. Some of those who ignored the order to report for registration by the German occupying forces were hanged on the city streets in order to intimidate the Jewish population.

Almost all of Simferopol’s Jews were shot to death. Many of the victims had been betrayed to the Germans by the local population.